421 
Embryo of Cryptomena Japonica. 
their development, they deviate very little out of the straight line towards 
the female prothallium. As shown in Fig. 8, the cells of the nucellar 
tissue through which the tube passes become disorganized, and are 
probably absorbed by the developing tube. There are usually five or 
six pollen-tubes present, and by the time they reach the female pro- 
thallium, the upper portion of the nucellus has a very disorganized 
appearance (Fig. 7). As the tube advances the tube-nucleus is always 
found near the tip. 
Soon after the penetration of the tube both the nuclei within it enlarge 
considerably and advance with the growing tube. The generative nucleus 
is always a little in the rear of the tube-nucleus. Before the tube has 
penetrated very far the generative nucleus divides, and the young pollen- 
tube has now three free nuclei. Of the two nuclei derived from the 
generative nucleus, it is impossible to say which is the stalk- and which 
is the body-nucleus, as they are of equal size. One of them, however, 
very soon enlarges and becomes surrounded by a dense zone of granular 
cytoplasm, in which innumerable starch-granules are imbedded. The 
future activity of this nucleus proved it to be the body-nucleus, and 
the sister-nucleus which failed to enlarge is no doubt the so-called 
stalk-nucleus. 
The body-nucleus eventually becomes several times the size of the 
stalk-nucleus, and, as it grows, the cytoplasm surrounding it becomes much 
more dense. A membrane is now formed at the periphery of the dense 
zone, and a distinct body-cell is organized, which becomes perfectly 
spherical. The thickness of the dense zone of cytoplasm within the body- 
cell-membrane is about half the diameter of the large, centrally situated 
nucleus as shown in Fig. 4. The tip of the tube now contains one large 
spherical cell and two free nuclei. These three structures always lie near 
each other in a central strand of cytoplasm. The relative positions and 
size of these structures is shown in Fig. 4. The lower free nucleus (marked 
t.n.) is the tube-nucleus. Immediately above this is the stalk-nucleus 
(marked s.n.), and slightly in the rear is the large body-cell (marked b.c.). 
These three structures remain in close proximity to each other till about 
the middle of June, when the two male cells are organized. When fully 
mature, the nucleus of the body-cell is at least four times the size of the 
tube- or stalk-nuclei. It contains a very large nucleolus, and the chromatin 
at this time appears in the form of coarse, deeply staining granules 
suspended on threads of linin. The cytoplasm surrounding the body- 
cell and the tube- and stalk-nuclei is very coarsely granular, but free from 
starch. Within the body-cell large quantities of starch-grains are always 
present. 
It takes the tube about three or four weeks to reach the female 
prothallium, and during this period the body-cell undergoes no more 
G g 2 
